This proposal is in response to RFA-AA-07-005. Prior to the disappointing findings of Project MATCH, patient-treatment matching was viewed as a promising paradigm for increasing alcohol treatment effectiveness. The paucity of findings to support matching treatment modality to patient attributes in Project MATCH led researchers largely to abandon this paradigm. However, further study has used observer ratings of therapist interventions from Project MATCH to successfully identify 3 patient-treatment interactions and to demonstrate how specific matches and mismatches between patient attributes and therapist interventions predict treatment effectiveness. Specifically, findings have shown that post treatment alcohol use is associated with the occurrence of a match or mismatch between the level of therapy structure in relation to the level of patient reactance (i.e., opposition to influence from others), and with mismatches between the level of therapist confrontation in relation to the level of patient reactance and patient trait anger. What remain unknown are the mechanisms of action through which these match and mismatch effects exert their influence on alcohol use. The objective of the proposed research is to study potential mechanisms of action that underlie these effects. Drawing on both the theories behind these effects and the extant literature on purported mechanisms of action in behavioral therapies, this research will use observer-based ratings of alcohol treatment sessions to examine the roles of (1) cognitive change in beliefs about alcohol use, (2) change talk, and (3) in-session resistance as potential mechanisms. The project will sample patients from both the aftercare (n=138) and outpatient (n=138) arms of Project MATCH. Linear regression and structural equation modeling will be used to test if the purported mechanisms mediate the match and mismatch effects on the frequency of post treatment alcohol use. The proposed research design will attend to the temporal sequence of when variables are measured to increase the likelihood that observed mediation effects will meet essential criteria for mechanisms of action. If positive, the results of this study will validate the importance of these patient-treatment match and mismatch effects, will provide valuable insights into the active ingredients of behavioral treatments, and will provide compelling evidence on which to base a prospective randomized clinical trial that examines these matching effects in treatments for alcoholism. If positive, the results of this study will validate the importance of patient-treatment match and mismatch effects, will provide valuable insights into the active ingredients of behavioral treatments, and will provide compelling evidence on which to base a prospective randomized clinical trial that examines these matching effects in treatments for alcoholism. [unreadable] [unreadable] [unreadable]